1. Field of the Invention
The present invention is related to coupling systems for lockably connecting one machine tool to another, particularly to such a coupling system for releasably connecting a tool to a toolholder. Still more particularly, the present invention is related to a coupling system in which rotatable locking fingers selectively function to secure the tool to the toolholder as well as assist release of the tool from the toolholder.
2. Description of the Prior Art
It is well known in the machine tool art that toolholders of lathes, presses, or other industrial machines utilize interchangeable tools which are suited for various operations on workpieces. Generally, the tool is manually connected with the toolholder utilizing some form of releasable coupling system that locks the tool to the toolholder. Because of the nature of the forces encountered during industrial processes, the connection of the tool with the toolholder must be strong and stable, yet because of production cost concerns, the connection must be effected easily and quickly. Most commonly, the toolholder and the tool have portions contoured to form a mated male-female interrelationship (usually in the form of reciprocal cylindrical or frusto-conical shapes), the toolholder being provided with a locking mechanism having locking members which selectively radially move so as to interferingly engage the tool, thereby locking it with respect to the toolholder.
In the prior art there have been a number of attempts to provide a suitable coupling system for machine tools. These devices can be divided into two broad classes based upon the type of locking mechanism utilized: those having locking members in the form of balls, and those having locking members in the form of plungers.
The first class of coupling systems utilizes a toolholder having locking balls which selectively engage respective sockets on the tool so as to lock the tool with respect to the toolholder. Position of the locking balls for selective engagement with the tool is radially regulated by contact of the locking balls with a cam surface located on a bolt that is slidable within an axial bore of the toolholder. Examples of this first class of coupling systems are disclosed in U.S. Pat. Nos. 4,680,999 and 4,932,295.
The second class of coupling systems utilizes a toolholder having locking plungers which selectively engage a complementary shoulder of the tool to thereby lock the tool to the toolholder. U.S. Pat. Nos. 393,511, 4,684,301 and 4,850,765 are examples of coupling systems in which the locking plungers slide radially into or out of engagement with the tool in response to movement of a control member. U.S. Pat. Nos. 3,490,333, 3,791,257, 4,135,848, 4,226,562 and 4,844,671 are examples of coupling systems in which the locking plungers include arms which are pivotally connected to the toolholder; slidable movement of a bolt axially disposed within the toolholder cams against the arms, causing radial movement of the locking plungers into or out of engagement with the tool.
In each of the foregoing examples of the prior art, one or more locking members connected with the toolholder are caused to radially move into or out of engagement with the tool in response to movement of a control member. However, each of these structures require a number of laterally disposed internal components to effect retraction and engagement by the locking members, thereby limiting the minimum cross-section of the locking member, and, consequently, the toolholder. Such locking mechanisms in which the locking members are separately disposed across the cross-section of the toolholder require smaller sized components, resulting in compromised reliability and strength in situations involving smaller diameter tools. Further, none of the prior art devices address the issue of effecting removal of the tool from the toolholder after the locking members of the locking mechanism have retracted, a problem of great concern when the tool and toolholder have been precisely mated at very close tolerances.
Accordingly, what is needed is a coupling system for machine tools which is structured to provide a locking mechanism having substantial sized locking members even in applications involving small diameter tools, the coupling member further providing for positive assist to separate the tool from the toolholder during disengagement of the locking members with respect to the tool.